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Mortality

Introduction

Major impediments to producing a complete picture of Indigenous mortality in Australia are the incomplete identification of Indigenous status in death records and the experimental nature of the recently adopted population estimates [1]. As a result, the 2,767 deaths registered in 2010 where the deceased person was identified as Indigenous is certainly an underestimate of the actual number of Indigenous deaths.

The extent to which the number of Indigenous deaths is under-estimated is not available for recent years, however, even though the ABS does make adjustments to the number of registered deaths in preparing their estimates of life expectancy [1]. It is likely that these adjustments are in line the ABS’s assessment of the completeness of recording of Indigenous deaths in 2006-2007, which was based on a comparison of deaths in those years with Indigenous status reported in the 2006 census [2]. Based on this comparison, the ABS estimated that the Australia-wide level of Indigenous identification in deaths notifications in 2006-2007 was 92% [2], a level much higher than previous estimates (around 56%) [3].

The estimated completeness of identification of Indigenous people in death registrations has improved since the 1990s, mostly because of improvements in NSW and Qld, but there is still be some doubt about the actual levels of identification [1]. As a result, the ABS notes that caution should be exercised in the interpretation of the estimates of Indigenous mortality, particularly estimates of trends over time. This caution is reflected in recent ABS publications that do not include detailed tables of Indigenous deaths, nor information about overall death rates. As a result, there is no consistency about the extent of information available for recent years. Reflecting this, readers should be aware that the following sections vary in terms of the years to which they relate.

Age-standardised death rates

After adjusting for the differences in the age structures of the Indigenous and non-Indigenous populations, the overall death rate for Indigenous people in 2004-2008 was 1.8 times the rate for non-Indigenous people (Table 5) [5]. For NSW, Qld, WA, SA and the NT – the jurisdictions with adequate levels of Indigenous identification – the rate for Indigenous people and the Indigenous:non-Indigenous rate ratios were slightly higher. The rates for Indigenous people were highest in WA (1,673 per 100,000) and the NT (1,582 per 100,000).²

Between 1991 and 2008, there was a 25% reduction in the death rates for Indigenous people in WA, SA and the NT; most of this decline can be attributed to the declines of Indigenous deaths in WA and the NT [5]. The decrease was greater among Indigenous females (27%) than among Indigenous males (23%). There were also reductions for non-Indigenous males and females, so there was no decrease in the rate ratios.

Expectation of life

In 2009, the ABS revised its estimates for expectation of life at birth for Indigenous people [2]. After adjustment for the underestimate of the number of deaths identified as Indigenous, the ABS estimates that Indigenous males born in 2005-2007 could expect to live to 67.2 years, 11.5 years less than the 78.7 years expected for non-Indigenous males (Table 6). The expectation of life at birth of 72.9 years for Indigenous females in 2005-2007 was almost 10 years less than the expectation of 82.6 years for non-Indigenous females.

These revised estimates are significantly higher than previous estimates. Importantly, comparisons between the original and revised estimates should not be interpreted as a change in Indigenous life expectancy, but should be seen as the result of a revision in statistical methods used to calculate life expectancy [2].

Age at death

For those jurisdictions with reasonable information about Indigenous deaths, the median age at death ³ in 2010 for Indigenous males ranged from 50.8 years for those living in the NT to 58.3 years for those living in NSW [1]. These levels were around 20 years less than those for non-Indigenous males, which ranged from 64.9 to 79.6 years. The median age at death for Indigenous females in 2010 ranged from 55.4 years for those living in the NT to 67.1 years for those living in NSW. These levels were also around 20 years less than those for non-Indigenous females, which ranged between 75.2 and 84.9 years.

In 2006-2010, age-specific death rates were higher for Indigenous people than for non-Indigenous people across all age-groups, but the rate ratios were highest in the young and middle adult years (Table 7) [1]. (The rate ratios, based on the numbers of deaths registered, vary according to the levels of Indigenous identification (see above).)

Infant mortality

The infant mortality rate (IMR) is the number of deaths of children under one year of age in a calendar year per 1,000 live births in the same calendar year [1]. For those jurisdictions with reasonable information about Indigenous deaths in 2008-2010, the highest Indigenous IMR occurred in the NT and the lowest in SA (Table 8). These rates are considerably higher than those for non-Indigenous people in these jurisdictions.

In the five-year period from 2004 to 2008, Indigenous infants most commonly died from ICD ‘conditions originating in the perinatal period’, including birth trauma, disorders relating to foetal growth, and from complications from pregnancy, labour and delivery [5]. Indigenous infants died from ‘conditions originating in the perinatal period’ at twice the rate of non-Indigenous infants (4.4 compared with 2.1 per 1,000). The second most common cause of infant death was ICD ‘signs, symptoms and ill-defined conditions’, which includes sudden infant death syndrome (SIDS); Indigenous infants died at more than four times the rate of non-Indigenous infants (and, for SIDS alone, almost three times the rate).

From 1991 to 2008, there have been significant declines in IMRs for Indigenous and other infants in WA, SA and the NT [5]. The Indigenous IMR declined from 24.5 per 1,000 in 1991 (compared with 5.7 per 1,000 for other infants) to 9.2 per 1,000 in 2008 (2.8 per 1,000 for other infants). The rate ratio decreased from 4.3 in 1991 to 3.2 in 2008.

Causes of death

For deaths identified as Indigenous in 2004-2008, the ICD group ‘diseases of the circulatory system’ (more commonly known as cardiovascular disease, which includes heart disease and stroke) was the leading cause of death for Indigenous people living in NSW, Qld, WA, SA and the NT, (543 per 100,000 population) (Table 9) [6]. This was followed by neoplasms (cancer) (268 per 100,000) and respiratory diseases (152 per 100,000). For all major causes of death, Indigenous people died at a higher rate than non-Indigenous people within these jurisdictions.

In 2009, the leading specific causes of death differed for Indigenous males and females [7]. The two leading specific causes of death were ischaemic heart disease followed by diabetes for Indigenous male and females; intentional self-harm (suicide) was the third leading cause of death for Indigenous males and chronic lower respiratory diseases for Indigenous females. Ischaemic heart disease was also the leading cause of death for non-Indigenous people in 2009. For non-Indigenous males, the next most common cause of death was lung and related cancers, followed by stroke. For non-Indigenous females, the next most common causes were stroke followed by ICD ‘dementia and Alzheimer’s diseases’.

Maternal mortality

In Australia in 2003-2005 (the most recent period for which detailed data are available), six (10%) of the 60 maternal deaths where Indigenous status was known were of Indigenous women (Indigenous status was not reported in 8% of the deaths) [8].

Reflecting the higher rate of confinements among Indigenous women, the maternal mortality ratio for Indigenous women in 2003-2005 was 21.5 deaths per 100,000 confinements, almost three times higher than the ratio of 7.9 per 100,000 for non-Indigenous women (Table 10) [8]. For direct maternal deaths, the ratio of 7.2 per 100,000 for Indigenous women was twice the ratio of 3.6 per 100,000 for non-Indigenous women.

Avoidable mortality

Avoidable mortality refers to deaths that could have been prevented with timely and effective health care, including early detection and effective treatment, and appropriate modifications of lifestyle behaviours (such as quitting smoking) [5].

In the five-year period from 2004 to 2008, there were 6,443 deaths of Indigenous people aged 0-74 years from avoidable causes (5.5% of all deaths from avoidable causes) in NSW, Qld, WA, SA and the NT [5]. Almost three-quarters (72%) of all Indigenous deaths were from avoidable causes (compared with 66% of non-Indigenous deaths).

Indigenous males died from avoidable causes at 3.3 times the rate of non-Indigenous males (631 and 189 per 100,000, respectively), and Indigenous females died from avoidable causes at 3.8 times the rate of non-Indigenous females (397 and 104 per 100,000, respectively) [5]. Indigenous males and females aged 35-44 years died from avoidable causes at 5.2 and 5.6 times the rate respectively of non-Indigenous males and females.

The age-standardised rates of avoidable deaths among Indigenous people were highest in the NT (772 per 100,000) and WA (688 per 100,000), and lowest in NSW (356 per 100,000) (Table 11) [5]. Indigenous people died from avoidable causes at 3.5 times the rate of non-Indigenous people in NSW, Qld, WA, SA and the NT.

In 2004-2008, the most common conditions contributing to avoidable deaths among Indigenous people in NSW, Qld, WA, SA and the NT were ischaemic heart disease (19%), cancer (17%), diabetes (9.5%), and suicide (8.0%) [5]. The death rates from avoidable causes were around twice as high for Indigenous people than for non-Indigenous people for cancer and suicide, four times as high for ischaemic heart disease, and 13 times as high for diabetes.

Between 1997 and 2008, there were significant declines in the death rate from avoidable causes for Indigenous people in WA, SA and the NT, from 939 per 100,000 in 1997 to 751 per 100,000 in 2008 (compared with 206 per 100,000 in 1997 and 139 per 100,000 in 2008 for non-Indigenous people) [5]. Because of the decline in death rate for avoidable causes for non-Indigenous people, the rate ratios actually increased from 4.6 in 1997 to 5.4 in 2008.

The death rate from avoidable causes for Indigenous people living in NSW, Qld, WA, SA and the NT also decreased in eight-year period from 2001 to 2008, from 597 per 100,000 in 2001 to 499 per 100,000 in 2008 (compared with 177 per 100,000 in 2001 and 141 per 100,000 in 2008 for non-Indigenous people) [5]. There was a slight increase in the rate ratio from 3.4 in 2001 to 3.5 in 2008.

References

1. Australian Bureau of Statistics (2011) Deaths, Australia, 2010. Canberra: Australian Bureau of Statistics
2. Australian Bureau of Statistics (2009) Experimental life tables for Aboriginal and Torres Strait Islander Australians: 2005-2007. Canberra: Australian Bureau of Statistics
3. Australian Bureau of Statistics (2006) Deaths, Australia, 2005. Canberra: Australian Bureau of Statistics
4. Australian Institute of Health and Welfare (2011) Principles on the use of direct age-standardisation in administrative data collections: for measuring the gap between Indigenous and non-Indigenous Australians. Canberra: Australian Institute of Health and Welfare
5. Australian Institute of Health and Welfare (2011) Aboriginal and Torres Strait Islander health performance framework 2010: detailed analyses. Canberra: Australian Institute of Health and Welfare
6. Steering Committee for the Review of Government Service Provision (2011) Report on government services 2011: Indigenous compendium. Canberra: Productivity Commission
7. Australian Bureau of Statistics (2011) Causes of death, Australia, 2009. Canberra: Australian Bureau of Statistics
8. Sullivan E, Hall B, King J (2008) Maternal deaths in Australia 2003-2005. Canberra: Australian Institute of Health and Welfare

Endnotes

2. The estimate for WA includes unusually high numbers of Indigenous deaths registered in 2007 and 2008, so should be interpreted with caution.

3. The median age at death is the age below which 50% of people die. Because the measure partly reflects the age structures of the respective populations, it is a less precise measure than age-specific death rates, which are summarised below.